At a depth of more than a few meters, the ground remains at a relatively constant temperature year round ? somewhere between 7 and 21 degrees centigrade. That temperature is lower than the air temperature in the summer, and higher ? often a LOT higher ? than the air temperature in the winter. Geothermal or ?earth energy? heat pumps take advantage of this temperature difference to heat and cool your house.

The system has three parts: an ?earth connection? segment, a heat pump, and a circulation system.

The earth connection segment, commonly called the ?loop?, consists of a series of pipes sunk into holes drilled into the ground. The loop is a closed system that circulates a refrigerant liquid between the ground outside, and the heat pump located in your house.

In the winter, the system runs in one direction, picking up heat from the ground, and concentrating it via the heat pump. This heat is then transferred to a circulation system that distributes the heat around your house.

In the summer, the system runs in the opposite direction. The heat pump refrigerates the circulation system in your house, concentrating the heat and dumping it into the ground through the earth connection loop.

Most systems operate using water or a water-antifreeze mixture; systems like ours that employ refrigerant are known as ?direct expansion? or DX systems.